By Tim Gay
The following is excerpted from The Physics of Football.
What can a kicker or punter do to improve his accuracy? Unlike linemen, who are a deliberative, logical, and pensive group given to quiet self-introspection, these guys, as a class, are as superstitious as all get-out. Over the years, a large body of folklore has built up on ways to improve accuracy. Specific techniques of kicking, prescriptions for holders, and detailed requirements for shoes, not to mention the size and placement of rabbit’s feet and lucky tattoos, are hotly debated. Several years ago, before the advent of the infamous “K” ball (which can be removed from its factory wrapper only in the presence of an official), Sports Illustrated ran an article on methods kickers used to doctor balls prior to games. The list included repeated inflation and deflation, immersion in ice water, microwaving, and virtually every other treatment (or mistreatment) imaginable except, perhaps, “sautéing…and plating them up with a nice port wine reduction.” What works and what doesn’t? What does physics have to say?
First, physics (and common sense) says: Hit the ball square. The ball will travel, at least initially, in the same direction as that of the force vector the foot applies to the ball. Let’s say you want to make a 50-yard field goal from the left hash mark. This requires a directional accuracy of better than 7 degrees. Assume that you’re kicking the ball straight ahead and that the force of your foot on the ball is perpendicular to the surface of the ball where contact is initially made. This means that the impulse delivered to the ball must be within three-eights of an inch of the ball’s centerline, or equator.
Such directional accuracy is more easily accomplished with a soccer-style kick – where the ball is kicked off the side of the foot – than with the straight-ahead style. Accuracy is accomplished in the soccer-style kick by angular placement of the foot perpendicular to the plane of the leg motion, whereas accuracy with a straight-ahead kick requires side-to-side spatial placement accuracy. When the kicker or punter is swinging his leg through a 90-degree arch with a terminal foot speed of 75 feet per second, it is much easier to orient the angle of his foot than to make sure the tip of his toe passes through a needle’s eye with less than a half-inch radius. This simple physiological/geometrical truth is responsible for the almost complete disappearance of straight-ahead kickers from pro and college football.
Before soccer-style kicking became popular back in the 1980s, placekickers would use shoes with squared-off toes to achieve the same effect. Perhaps the prime example of this was Tom Dempsey. Born with only half of a right foot, Dempsey had a special shoe with a very broad, flat front surface. Jason Elam, on the other hand, who tied Dempsey’s record nearly three decades later, kicked soccer-style.
Tim Gay is a Professor of Physics at the University of Nebraska – Lincoln. In addition to enlightening football fans with his lectures and book, The Physics of Football, Gay studies polarized electrons, teaches college physics, and recently starred as rocker Tommy Lee’s advisor in the reality TV show "Tommy Lee Goes to College."